
class _Stack:
	"""
	通过数据格式List,实现Stack
	"""
	def __init__(self):
		self.items = []

	def push(item):
		return self.items.append(item)

	def pop():
		return self.items.pop()

	def peek():
		return self.items[-1]:
	
	def size():
		return len(self.items)

	def is_Empty():
		return True if size() == 0 else False


